A hyperbaric chamber is conventionally used in the treatment of a variety of medical ailments by creating a high pressure environment in which a patient breathes a high concentration of oxygen. Hyperbaric chambers are used for a variety of medical purposes, including treating gangrene, decompression sickness and skin grafts. Since the patient is breathing a high concentration of oxygen, the healing process and healing times are purportedly improved. Conventional hyperbaric chambers usually include a pressure type compartment large enough to accommodate at least one person and a system for pressurizing the chamber. Typically, a patient in a hyperbaric chamber will breathe the same oxygen used to pressurize the chamber, or air is used to pressurize the chamber and oxygen is provided to the patient via a mask or hood assembly. Exhaled air which contains oxygen is exhausted from the hyperbaric chamber and is wasted. The oxygen is usually provided from a bank of high pressure oxygen cylinders located outside of the hyperbaric chamber. The oxygen is brought into the chamber through one or more tubes which penetrate the pressure containing wall of the hyperbaric chamber.
Conventional high pressure medical oxygen concentrators are usually limited to commercial installations where substantial floor space must be dedicated to supply a hospital's oxygen needs. Conventional high-pressure oxygen concentrators, cryogenic oxygen systems or banks of pressurized bottles are expensive, physically large and cumbersome, non-portable and require considerable maintenance. Conventional high-pressure oxygen concentrators are not suitable for domestic home market use because of their bulk, lack of portability and expense.
A number of patents have been granted over the years protecting various designs of hyperbaric chambers, and systems for handling oxygen-containing gases.
Gamow et al., U.S. Pat. No. 4,974,829, discloses a portable hyperbaric chamber. The chamber is designed for use by mountaineers and the like. The hyperbaric chamber consists of a balloon-like enclosure capable of maintaining a pressure from 0 to 10 psi above ambient. The device is pressurized by an air compressor 9 which delivers air into the interior of the enclosure. The oxygen content of internal air is replenished from a tank of compressed oxygen 13. Excessive carbon dioxide and water are removed by a chemical scavenger 10 through which internal air is circulated by a blower 11. Excess pressure is vented through an exit port 12 which optionally includes a differential pressure valve.
Gamow's second U.S. Pat. No. 5,109,837, is a continuation-in-part of the '829 Gamow patent. This patent discloses (see FIG. 6C) a hyperbaric chamber for treating a patient 610 which includes a closed-circuit oxygen scuba rebreather 611 for use in providing oxygen enriched air to the patient. As shown in FIG 6C, rebreather 611 appears to draw air from inside the hyperbaric chamber. Pressure inside the hyperbaric chamber is maintained by inflating the chamber with air from a compressed air tank 68. The patent specification notes that the compressed air tank could be replaced with a "pump operable by hand, foot, or other power source". Various other less relevant closed-circuit breathing systems are shown in the other drawings (for example, FIGS. 8, 9A and 9B).
Athayade et al., U.S. Pat. No. 5,082,471, discloses a shelter which includes a life support system. The shelter could be used, for example, to protect its inhabitants against a poison gas attack. The chamber includes a carbon dioxide removal unit which draws air from the interior of the chamber, passes the air through a scrubbing unit, and reintroduces the scrubbed air into the chamber. The carbon dioxide scrubbing unit may include a molecular sieve (see the last portion of column 5).
Reneau, U.S. Pat. No. 4,633,859, discloses a hyperbaric chamber in which an inert gas is used as a pressurized gas source 20A. A throttling valve 20C is connected between the gas source and the interior of the hyperbaric chamber. An outlet valve 20F allows gas to exhaust from the chamber. Pressure inside the chamber is controlled by actuating throttling valve 20C and valve 20F. Preferably, the pressure controller monitors the rate of pressure build-up after valve 20F has been closed and regulates valve 20C to hold pressure at a preset value (column 4, first paragraph). A patient inside the chamber breathes gas delivered from a pressurized oxygen source 40A and a pressurized air source 40B which are delivered into a mask 40I.
Galerne, U.S. Pat. No. 4,227,524, discloses a hyperbaric chamber system which includes means for transferring patients from one place to another. The hyperbaric chamber system includes fittings which pass into the chamber from outside for carrying oxygen 33 and compressed gas 37 into the hyperbaric chamber. A secondary detachable chamber is provided to allow a person to be transported to a medical facility. The transportable chamber includes a system for removing carbon dioxide and a dehumidification system. The dehumidification system may include a molecular sieve. Galerne does not give much detail about the operation of the CO.sub.2 scrubber or the dehumidification system.
Hannum, U.S. Pat. No. 5,327,904, shows a small hyperbaric chamber which is pressurized with air. The air is pressurized by an air pump 13. The amount of air exiting the chamber is controlled by a chamber outflow control valve 37. It is not clear what role, if any, chamber outflow control valve 37 plays in regulating the pressure inside the hyperbaric chamber.
Henson, U.S. Pat. No. 5,263,476, discloses a sterile burn enclosure system which can be used to expose a patient to an atmosphere containing high concentrations of oxygen. The system includes means to control humidity, temperature and pressure within the enclosure. Oxygen is introduced into the enclosure from an external oxygen supply.